A critical value is a laboratory value that, if not acted upon promptly, may result in patient harm. Different healthcare regulatory and accrediting organizations have developed different definitions and requirements related to critical values. Common elements include: (1) A definition of which tests and values are defined as critical values (generally low or high abnormal results or positive qualitative results); (2) An organized system, described in one or more policies and procedures, on how a responsible party or caregiver is notified of a critical laboratory result. The system will define which responsible parties may accept critical results; (3) A policy and procedure on how critical results are communicated, including the steps needed to document critical value notification; (4) An acceptable time limit for communication of critical results.
Defining Critical Values
The definitions and requirements defined by The Joint Commission are among the most widely used concepts in the United States, likely because The Joint Commission accreditation has focused on the critical laboratory value notification process for many years. The Joint Commission defines a critical test result as “a test result that falls significantly outside the normal range and may indicate a life-threatening situation.” Certain practices such as call centers (for higher volume laboratories), read-back of critical values conveyed verbally, and documentation of time and date of notification and person notified have become widely used. Effective critical value systems improve patient safety, are agreed upon by laboratory and medical staff leadership, and can be implemented and executed as designed.
The Notification Process
People sometimes ask whether all steps taken for critical value notification of central laboratory results are necessary when testing is performed at the point of care (POC). The short answer is no. Going back to the principles above, the system should be effective in improving patient safety, clearly defined, and agreed upon by all stakeholders. In some cases, the person performing POC testing may be authorized, via institutional protocol or order set, to take action immediately on the results. For instance, in some insulin dosing order sets, the nurse performing glucose testing is authorized to change the insulin infusion rate or modify the glucose monitoring frequency based on results. A nurse performing POC international normalized ratio (INR) testing may be authorized by protocol to hold warfarin and order a plasma INR confirmation test. In these examples, the same type and extent of critical value notification may not be needed with POC compared to central lab tests.
Also unique to POC are limitations of some measurement technologies, such that POC programs may want laboratory confirmation to occur before providers take action on “pathological” values. The laboratory or health system may want POC end users to document that appropriate action was taken in response to a value defined as critical. In this context, the documentation does not serve the same purpose as critical value notification, but for convenience, the process may be described in a critical value policy or procedure.
As with critical value policies designed for the central lab, the protocols for critical value notification at the POC should maximize patient safety while considering institutional resources. For example, recognizing the harm caused by hospital-acquired hypoglycemia and understanding that dextrose/glucose is a benign therapy, many hospitals now ask that nurses give glucose and repeat bedside measurements rather than wait for laboratory confirmation of critically low glucose. In contrast, confirmation of critically high glucose values with a stat plasma glucose may still be required before large correction doses of insulin are given.
Going back to the question of whether the same process (e.g., telephone calls, readbacks) must be used for POC tests, calling a nurse to notify them of critical glucose after they had already taken action under an institutional protocol would consume resources without adding to patient safety. Thus the “critical value” policy of the laboratory may require documentation of an appropriate action taken rather than a name of an authorized provider who accepted the critical result. In other circumstances, the end user may not be authorized by protocol or scope of practice to take appropriate action in response to a critical value, in which case it would be reasonable to require documentation of the value being communicated to an authorized provider. In either case, the documentation system for POC testing often will differ from central laboratory processes and may involve adding a code or message to the device being used for testing rather than documenting the time, date, and name of a person notified of the result.
Implementing an Effective Policy
POC programs should ensure that expectations for critical value notification at the POC are clearly defined in a policy. Including this information in the laboratory critical value policy has the advantage of putting all information on critical values and related processes in one place. The critical value policy may define how each critical value at the POC is handled or may just indicate that POC critical values are handled by alternative mechanisms defined in procedures. This information could also be included in the institutional POC testing policy.
Having the policy or procedure clearly documented, and ensuring that the system is effective (e.g., auditing critical POC values for appropriate comments or codes), will prepare POC programs for regulatory and accrediting agency inspections. More important, thinking through the notification actions needed in response to critical POC values will ensure patient safety.
Brad S. Karon, MD, PhD, FCAP, is a professor of laboratory medicine and pathology at Mayo Clinic College of Medicine and Science in Rochester, Minnesota. +Email: [email protected]